You should really work something out with your roommate/s. Let them know how serious this situation is, and that if anything like this happens again, and it's at all their fault, they take care of vet bills or replacement bills.
With expensive animals, and living animals, it should be in writing.
I really hope he survives, and that something good can come out of this. I'm really sorry this had to happen to you. This is part of the reason I hate alcohol, it turns people into idiots, who couldn't care less about an animals life.
Good luck! I've got all my hopes out for you.